Update, 9:59 a.m. Jan. 27: A freezing rain advisory is now in effect for all of northern Illinois.
The advisory, in effect from 11 a.m. until 7 p.m. today, replaces the winter storm watch that had previously been issued by the National Weather Service in Chicago.
The freezing rain is expected to start midday, with ice accumulations up to a couple tenths of an inch expected.
"Pavement and soil temperatures are below freezing, so any liquid precipitation will likely freeze on contact and result in icy and dangerous travel conditions on untreated roadways," National Weather Service officials said in their advisory statement. "Walkways could also turn to sheets of ice, making walking difficult and potentially dangerous."
Original story, from Jan. 26: A winter storm watch—with the potential for an ice storm—has been issued for all of northern Illinois from Sunday morning through late Sunday night.
The National Weather Service in Chicago says there is the potential for "significant ice accumulation in excess of a quarter of an inch."
According to a multimedia weather briefing posted Saturday morning, there is at least an 80 percent chance of freezing rain Sunday, with a 50 to 70 percent chance of at least a tenth of an inch of ice accumulation across northern Illinois.
The National Weather Service in Chicago warns that untreated roads and sidewalks could quickly become covered in ice. Additionally, "ice accumulating on tree limbs and power lines will weigh them down and, with increasing wind, could result in power outages."